Effects of concentrate level and grazing system on the performance of beefcattle grazing autumn herbage

To identify strategies for improving the growth rate of cattle grazing autu mn grass, the effects of grazing management and supplementation with concen trates were quantified. Continental crossbred steers (n = 60; mean live wei ght 504 kg) were blocked according to live weight and assigned at random fr om within blocks to six treatments. The treatments were: an allowance of 11 kg grass dry matter (DM) per head daily, supplemented with 0 (control), 2. 5 or 5 kg concentrates, an allowance of 11 kg grass DM per head daily witho ut concentrates but managed as leaders or followers within a leader/followe r system and concentrates offered ad libitum (no grass). Grass allowances w ere based on the yield when cut to 4-cm stubble. Animals were offered grass in groups, according to treatment, with herbage allowances adjusted daily while concentrates were offered individually. Grass intake was estimated as the difference between the pre- and post-grazing yields. The experiment be gan on 22 August and had a mean duration of 84 days. Supplementation with c oncentrates decreased grass intake but increased final live weight (P < 0.0 01), carcass weight (P < 0.001), carcass conformation score (P < 0.001) and carcass fat score (P < 0.05). The leader animals had higher (P < 0.001) an d the follower animals had lower (P < 0.001) carcass gains compared with th e control group of steers. The carcass gain response (kg/day) to concentrat es (Y) was linearly related to concentrate allowance (X) according to the e quation: Y = 0.0925X + 0.3874 (R-2 0.54). When supplemented with 5 kg conce ntrates, grass-fed animals had similar growth rates to the ad-libitum conce ntrate treatment. It is concluded that supplementing cattle, grazing autumn grass, with concentrates supported carcass growth rates closer to their po tential than altering the grazing management strategy.